Ring traveler and method for producing the same

ABSTRACT

The ring traveler ( 10 ) according to the invention has a noncoated core ( 20 ) which consists of iron material and which is provided with an, if appropriate, multipart nitrided edge layer ( 23; 24 ) at least in the region of the running surfaces ( 1 ) with which said core slides on a ring of a ring spinning or ring twisting machine.

This application is a national stage application, according to ChapterII of the Patent Cooperation Treaty.

The invention relates to a method for producing a ring traveler for ringspinning or ring twisting machines and to a ring traveler as claimed inclaims 1 and 7 respectively.

Ring travelers of ring spinning and ring twisting machines are moved ata high rotational speed (30 m/s to 50 m/s) on rings of the correspondingring spinning or ring twisting machines. Both the contact surfacebetween ring traveler and ring and the contact surface between ringtraveler and thread are subjected to a high degree of wear. To increaseproduction, however, increasingly higher running speeds of the ringtravelers are required. By longer service lives being achieved, thecosts are at the same time to be lowered.

It has been possible, in recent years, to improve the running andoperating properties of ring travelers markedly by these being coatedwith appropriate materials. However, it has not been possible hithertoto improve the wear resistance at the thread passage.

U.S. Pat. No. 4,677,817 discloses a ring traveler having a ceramic layerwhich gives the ring traveler greater hardness and improved heat andcorrosion resistance. This known ring traveler has markedly reducedoperating costs due to the improved running and operating properties.However, the relatively high outlay in terms of production has anadverse influence on costing.

The object of the present invention is, therefore, to provide a ringtraveler for ring spinning or ring twisting machines, which, on the onehand, has further-improved running and operating properties and, on theother hand, can be produced at a reduced outlay. A method for producingthis ring traveler is also to be specified.

This object is achieved by means of a method and a ring traveler whichhave the features specified in claim 1 and claim 7 respectively.

A ring traveler according to the invention has a noncoated core whichconsists of iron material and which has an, if appropriate, multipartnitrided edge layer at least in the region of the running surfaces withwhich said core slides on a ring of a ring spinning or ring twistingmachine or in which the thread is guided.

Instead of a layer, for example a ceramic or phosphate layer, beingapplied to the core and, if appropriate, being remachined, atconsiderable outlay, said core is subjected, at least partially, to anitriding treatment, during which heat energy and a nitriding agent asactive medium are supplied to the core.

Embrittlement and a considerable reduction in the elasticity of thetreated material are known to occur during nitriding treatment. By thecomposition of the nitriding agent being controlled according to theinvention and by an appropriately selected treatment time, theelasticity of the ring traveler, which is necessary so that the lattercan be attached, free of deformation, onto spinning rings, can bemaintained.

The core is heated to a temperature in the range of 450° C.-600° C.,preferably to a temperature close to 550° C., and is maintained in saidtemperature range for 3-60 hours, preferably for about 24 hours. Thenitriding agent may be supplied in the form of a gas, liquid or plasmapreferably consisting of NH₃ and N₂ components. Regions in whichnitriding treatment is not to take place are, for example, covered.

The nitrided edge layer of the ring traveler core consists of aconnecting layer without an additional diffusion layer, of a connectinglayer with an additional diffusion layer lying radially on the inside oronly of a diffusion layer. The connecting layer has preferably athickness of 0.1 μm-30 μm and the diffusion layer a thickness of 1μm-2000 μm.

Preferably, the active medium has, in addition to the nitrogencomponents, sulfur components and/or carbon components. By sulfurcomponents and/or carbon components being admixed, the coefficient offriction can be reduced. At the same time, the thicknesses of theconnecting layer and of the diffusion layer can be coordinated, asrequired.

When small thicknesses of the connecting layer are selected, only slightvariations in the roughness of the core surface are obtained.

In preferred refinements of the invention, the surface of the ringtraveler is additionally polished before and/or after the nitridingtreatment. Ring travelers exposed to high chemical stress are preferablyreoxidized.

In so far as a core made from a heat-treated steel is used, onlynegligibly small changes in dimension occur during the nitridingtreatment.

The ring travelers according to the invention have substantiallyimproved operating properties, in particular an increased travelerservice life and increased indentation resistance at the thread passage.The functionally very important indentation resistance in the threadpassage with a mechanical and/or chemical load was improved by 50%-200%,thus resulting in an improvement in the quality of the processed yarn.Furthermore, by virtue of the increased chemical resistance, yarncontaminations due to corrosion products which previously occurredduring the processing of revived and chlorine-containing fibers areavoided. Moreover, because of the good sliding properties, no or onlyslight fiber lubrication is required.

Furthermore, the ring travelers can be produced at lower outlay andadapted to individual requirements which may possibly arise.

Ring travelers according to the invention may be used both in spinningmills and in twisting mills. Their good running properties, such as, forexample, good sliding and low wear, are implemented particularlyadvantageously in cooperation with steel rings, but they may also beused on other rings, such as, for example, on sintered, burnished orcoated rings.

The ring traveler according to the invention is explained in more detailbelow with reference to exemplary embodiments shown in the purelydiagrammatic drawings in which:

FIGS. 1a-1 f show various embodiments of ring travelers,

FIG. 2 shows a section through the core of a ring traveler before theprocessing of the latter and

FIGS. 3-5 show a section through the core of ring travelers after theprocessing according to the invention.

FIGS. 1a to 1 f show ring travelers 10 a, . . . , 10 f in variousembodiments already described in WO 99/49113. FIGS. 1a and 1 b showC-shaped ring travelers 10 a, 10 b, such as are used typically onT-flanged rings of ring spinning or ring twisting machines. By contrast,FIGS. 1c to 1 f show ear-shaped and hook-shaped ring travelers 10 c, . .. , 10 f. The ring travelers 10 c and 10 d are used on oblique-flangedrings, the ring travelers 10 e on flanged rings running conically andthe ring travelers 10 f on flanged rings running vertically.

Those regions of the ring travelers 10 a, . . . , 10 f which, duringoperation, form the running surfaces sliding on the flanged rings areidentified in each case by 1. In the case of the C-shaped ring travelers10 a, 10 b, because of their symmetric configuration both flanks a, bserve as running surfaces. In the case of the ear-shaped or hook-shapedring travelers 10 c, . . . , 10 f, the region 1 of the running surfacesis clearly determined by the shape.

Ring travelers 10 or 10 a, . . . , 10 f according to the invention maybe produced in the embodiments shown in FIG. 1a, . . . , if or in anyother desired embodiments.

A ring traveler 10 according to the invention has a noncoated core 20which consists of iron material and which has a nitrided zone at leastin the region 1 of the running surfaces with which it slides on a ringof a ring spinning or ring twisting machine, or in the region in whichthe thread is guided. The thread passage is located, in this case, inthose regions of the ring travelers 10 a, . . . , 10 f which aredesignated by 4.

For this purpose, the ring traveler 10 is subjected, at least partially,to nitriding treatment, during which heat energy and a nitriding agentas active medium are supplied to the core 20. In order to achieve assmooth surfaces as possible after the nitriding treatment, the ringtraveler 10 is polished preferably before the nitriding treatment.

The basic material of the core 20 is preferably an unalloyed orlow-alloy steel, preferably a nitriding steel. Preferably, a core 20consisting of a heat-treated steel is selected, in which only negligiblysmall changes in dimension occur during the nitriding treatment.Furthermore, the basic material of the core 20 preferably containsnitride-forming elements, such as chromium, vanadium, aluminum,molybdenum, manganese and/or nickel.

In addition to the choice of raw material (for example, heat-treatedsteel), the process parameters, such as the temperature profile (rampprofile of the heating, holding time and holding temperature, rampprofile of the cooling) and the composition of the nitriding agentinfluence the result of the nitriding treatment.

The core is heated in a furnace to a temperature in the range of 450°C.-600° C., preferably to a temperature close to 550° C., and ismaintained within said temperature range for 3-60 hours, preferably forabout 24 hours. The nitriding agent may be supplied in the form of agas, liquid or plasma preferably consisting of NH₃ and N₂ componentsand, if appropriate, also having H₂. In the case of the plasmatreatment, during which preferably pure nitrogen N₂ is used as thenitriding agent, nitrogen atoms are ionized in an evacuated chamber,after which they are attracted by the oppositely polarized surface 22 ofthe ring travelers 10 and bond with the iron to form iron nitride.

Ring travelers 10 treated according to the invention preferably have,after treatment, a surface 22 a with a black, blue, yellow or whitegloss.

Preferably, the active medium has, in addition to nitrogen components,sulfur components and/or carbon components. As a result, on the onehand, the coefficient of friction can be reduced and, at the same time,the formation of the nitrided zones can be influenced.

By virtue of the nitriding treatment described, an, if appropriate,multipart nitrided edge layer is formed in the core 20 of the ringtraveler 10 and is explained in more detail with reference to FIGS. 2 to5.

FIG. 2 shows a section through the core 20 of an untreated ring traveler10. It is clear that there is an unchanged basic material 21 over theentire core cross section.

FIG. 3 shows a section through the core 20 a of a treated ring traveler10, which has a thin edge layer consisting of nitrided basic materialand designated as a connecting layer 23, in which substantial diffusionsaturation has occurred.

FIG. 4 shows a section through the core 20 b of a more intensivelytreated ring traveler 10, which has a connecting layer 23 and, below thelatter, a further layer which consists of nitrided basic material andwhich is designated as diffusion layer 24. Nitrogen-enriched mixedcrystals and precipitated nitrides are contained in the diffusion layer24.

FIG. 5 shows a section through the core 20 c of a treated ring traveler10, which has only a diffusion layer 24 and no connecting layer 23.

The choice of the layer makeup is made according to the requirementprofile for the ring traveler 10. A hard connecting layer is preferablyprovided for ring travelers 10 with high running speeds. Preferably onlya relatively tough and yet relatively hard diffusion layer 24 isselected for ring travelers 10 which are exposed to relatively highforces, with a connecting layer being avoided.

The connecting layer preferably has a thickness of 0.1 μm-30 μm and thediffusion layer a thickness of 1 μm-2000 μm. The use of a connectinglayer with a thickness of 8 μm-12 μm and a diffusion layer with athickness of 100 μm-200 μm is particularly advantageous. By a smallthickness being selected or by the connecting layer being avoidedcompletely, material fractures can be prevented, which have hithertomade it impossible to employ this technology in this sector.

The layer thicknesses occurring as a result of nitriding treatmentdepend greatly on the steel composition and on the surface state of theuntreated ring travelers 10. Basically, a thick connecting layer isachieved in the case of a high nitrogen content and high temperaturesand a thin connecting layer is achieved in the case of a low nitrogencontent and low temperatures. The layer thicknesses or the diffusiondepths depend, at the same time, on the treatment duration.

Moreover, fine lightweight ring travelers 10 are treated for a shorterduration than coarse heavy ring travelers 10.

By sulfur components and/or carbon components being admixed, thecoefficient of friction can be reduced. At the same time, thethicknesses of the connecting layer and of the diffusion layer can becoordinated, as required.

If small thicknesses of the connecting layer are selected, only slightvariations in the roughness of the core surface 22 occur, so thatsubsequent polishing of the running surfaces can be avoided.Embrittlement of the core material is also avoided.

For optimizing the ring traveler 10, in preferred refinements of theinvention, the surface 22; 22 a of the core 20; 20 a is polished beforeand/or after the nitriding treatment.

Ring travelers 10 exposed to high chemical stress are preferablyreoxidized.

In the region of the running surface 1, primarily an inner face,designated by 3, of the ring traveler 10 must, of course, bewear-resistant and equipped with good sliding properties and thereforehave a nitrided layer 23; 24. The result of corresponding thread tensionmay be that the ring traveler 10 runs along, tilted laterally, on aring, so that it may prove advantageous also to provide both end faces 2with a nitrided layer 23; 24.

The nitriding treatment is preferably carried out for the entire ringtraveler 10, although it is also possible to provide only themechanically and/or chemically highly stressed regions with a nitridededge zone.

What is claimed is:
 1. A method for producing a ring traveler (10) forring spinning or ring twisting machines, which has a core (20)consisting of iron material, and comprising the step of subjecting atleast a portion of the core (20) to a funding treatment during whichheat energy and a nitriding agent as active medium are supplied to thecore (20), wherein the method includes the step of oxidizing the core(20) after the nitriding treatment.
 2. The method as claimed in claim 1,wherein the core (20) is heated to a temperature in the range of450-600° C.
 3. The method as claimed in claim 2, wherein the core (20)is maintained in said temperature range for 3-60 hours.
 4. The method asclaimed in claim 1, 2, or 3, wherein the nitriding agent is supplied inthe form of a gas comprising NH₃ and N₂ components, a nitrogen-enrichedliquid or a nitrogen-enriched plasma.
 5. The method as claimed in claim1, wherein the active medium includes components selected from the groupconsisting of sulfer components and carbon components.
 6. The method asclaimed in claim 1 wherein method includes the step of polishing thecore (20) before the nitriding treatment.
 7. The method as claimed inclaim 1, wherein method includes the step of polishing the core (20)after the nitriding treatment.
 8. A ring traveler (10) for ring spinningor ring twisting machines, comprising an iron core (20) wherein at leastone mechanically stressed part of the core (20) has a nitrided edgelayer (23, 24), and wherein the edge layer (23, 24) includes aconnecting layer (23) and a diffusion layer (24), whereby the connectinglayer (23) has a thickness of 8 μm-12 μm and the diffusion layer (24)has a thickness of 100 μm to 200 μm.
 9. A ring traveler (10) accordingto claim 8, wherein the mechanically stressed part of the core (20)comprises a running surface for the thread.
 10. A ring traveler (10)according to claim 8, wherein the mechanically stressed part of the core(20) comprises a surface running on the ring of the spinning or twistingmachine.
 11. The ring traveler (10) as claimed in claim 8 wherein theconnecting layer (23) contains components selected from the groupconsisting of sulfur and carbon.
 12. The ring traveler (10) as claimedin claim 8, wherein the surface (22) of the core (20) is polished and/oris provided with an oxide layer.
 13. The ring traveler (10) as claimedin claim 12, wherein the surface (22) of the core (20) is black, blue,yellow or white.
 14. The ring traveler (10) as claimed in claim 8,wherein the basic material (21) of the core (20) is nitriding steel. 15.The ring traveler (10) as claimed in claim 8, wherein the basic material(21) of the core (20) contains a nitride-forming element selected fromthe group consisting of chromium, vanadium, aluminum, molybdenum,manganese and nickel.